Talk about 20/20 hindsight: Thursday marks the 20th anniversary of the premiere of “That '70s Show,” a sitcom that itself looked back 20 years to the up-and-down 1970s.

The Fox series launched on Aug. 23, 1998, introducing viewers to a basement confab of Wisconsin high schoolers whose crazy conversations, rotating romances and awkward adventures – often accented with wafting pot smoke – made them a staple with viewers for eight seasons.

The youthful stars – Topher Grace (“BlacKkKlansman”), Laura Prepon (“Orange Is the New Black”), Mila Kunis (“The Spy Who Dumped Me”), Ashton Kutcher (“Two and a Half Men”), Wilmer Valderrama (“NCIS”) and Danny Masterson (“The Ranch”) – all graduated to successful entertainment careers. Kunis and Kutcher, whose characters were in a relationship on the show, later married in real life and now have two children.

Kurtwood Smith (Amazon's "Patriot"), who played cantankerous Red Forman, the father of Eric (Grace) and husband of Kitty (Debra Jo Rupp, “This Is Us”), reminisces about the show's lasting appeal and why it still resonates.

Jackie (Mila Kunis), left, and Kelso (Ashton Kutcher) were a couple on "That '70s Show" and they're now married in real life.(Photo: FOX)

Where there's smoke, there's ganja.

"That '70s Show" ingeniously incorporated marijuana, a more controversial topic 20 years ago than today, into its milieu. The network wouldn't allow the teens to be seen smoking marijuana, so the show created a weed-friendly vibe with wisps of smoke and an innovative and appropriately disorienting camera technique: a 360-degree sweep of high teens sitting in what became affectionately known as "The Circle."

"It was ingenious. Obviously, the kids were smoking pot and getting high, but they didn't want to show that," Smith says. "You saw smoke but never saw anybody smoking. The camera turning like that gave the feel of them being high without having to (show) that."

'That '70s Show' offered teenage nostalgia to an audience of young adults.

The series was set mid-decade in the '70s, with President Richard Nixon's resignation, the energy crisis and other real events available as historical references and joke fodder aimed at viewers who grew up in that decade.

It was a precursor to current and recent comedies anchored in past decades, including the 1980s ("The Goldbergs," "GLOW") and 1990s ("Fresh Off the Boat," "Everything Sucks!"), that appeal to the youthful longings of an adult audience.

Ironically, Smith thinks that setting the show in the past keeps it from seeming old.

"It was out of date to begin with. It's not going to be dated, because it's always been a period piece and was treated as such," he says. "You could watch it at any time in the future and it will still make sense."

'That '70s Show' suffered from a lesser version of 'M*A*S*H' syndrome, which only afflicts hit shows.

"M*A*S*H" ran 11 seasons, nearly four times the length of the Korean War it depicted. Similarly, the eight-season run of "That '70s Show" eclipsed the second half of the decade featured in the show, forcing squeezes and expansions of time.

"That was funny. Every once in a while, we'd have to say, 'Wait a minute. What year is this?' There would be particular things, actual historical events, taking place in the show and we'd have to try to figure that out," Smith says. "Time was flexible, shall we say."

Red's frank, crass language delighted fans.

Hard-working veteran Red had a cranky, crusty demeanor that shielded a slightly softer center, especially when it came to son, Eric. But his terms of endearment, calling Eric a "dumb---" and forever promising to, politely speaking, kick his derriere, helped earn him a place in the hearts of viewers.

"The first time I called him a dumb---, I remember thinking how funny that line was. When it came time to do it in the show, I was thinking, 'Just say the words,' because if I leaned on it at all, it would wreck the moment," Smith says. "It needed to come out easy and straight. That's what I did with it and it brought the house down."

"That '70s Show" ended its eight-season run with a New Year's Eve episode on the final day of the 1970s that featured many original cast members, including, in the foreground, Danny Masterson, left, Debra Jo Rupp, Ashton Kutcher and Kurtwood Smith. Wilmer Valderrama looks on from the stairs.(Photo: GREG GAYNE/FOX)

Fans, and Smith, would enjoy a reunion.

For Smith, who's planning dinner soon with Grace and recently attended a play starring Rupp, the biggest " '70s Show" get-together so far came when he made guest appearances on Netflix's "The Ranch," which starred Kutcher and Masterson (who was dropped from the show in 2017 in the wake of sexual-assault allegations that he has denied) and included a director, producer and props workers from "That '70s Show."

"Because of Ashton and Mila being married, Mila was around. It was great fun getting to see her and those babies. Amazing!" he said. "It really was like a school reunion."

The idea of an original-cast revival, a TV trend that includes "Will & Grace," "Roseanne" and "Murphy Brown," appeals to him, but nothing's planned, and the odds are long.

"I have people ask me about it all the time," he says. However, "I don't think, given everybody's schedule, that would happen. I think a lot of us would be in favor of that, but I can't speak for everyone."

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"That '70s Show," which made its debut 20 years ago, followed a group of friends navigating teenage life in Wisconsin. The show, featuring Laura Prepon, Topher Grace, Danny Masterson, Wilmer Valderrama, Ashton Kutcher and Mila Kunis, lasted for eight seasons before being canceled by Fox in 2006. Here's where a few of our favorites actors from the show are now. Fox

Kunis (with Kristen Bell and Kathryn Hahn) has found success in the movies, including the current "The Spy Who Dumped Me" with Kate McKinnon, "Bad Moms" (pictured) and "Black Swan." She also voices Meg Griffin on the long-running Fox animated series "Family Guy." STX Entertainment

Masterson starred in TBS's "Men at Work" for three seasons before heading to Netflix's "The Ranch" in 2016. In 2017, several women came forward alleging that Masterson had raped them. He denied the allegations and no charges have been filed, but Netflix announced late last year that he would no longer be on the series. Greg Gayne/Netflix